Fluted composite and related absorbent articles

ABSTRACT

An absorbent composite that includes a fibrous matrix having absorbent material dispersed in bands along the composite&#39;s length is disclosed. The bands define liquid distribution zones. On liquid contact, absorbent material swelling occurs and produces a wetted composite having flutes that include swollen absorbent material separated by distribution zones, regions of the composite that are substantially free of absorbent material. Absorbent articles that include the composite are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending international patentapplication No. PCT/US99/05998, filed Mar. 18, 1999, which is acontinuation-in-part of U.S. provisional applications No. 60/078,779,filed Mar. 19, 1998, No. 60/082,771, filed Apr. 23, 1998, No.60/082,790, filed Apr. 23, 1998, and No. 60/111,845, filed Dec. 11,1998, the benefit of the priority of the filing dates of which arehereby claimed under 35 U.S.C. §§120 and 119, respectively. Each ofthese applications is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to an absorbent composite and absorbentarticles that include the composite. The absorbent composite is a flutedabsorbent composite that includes superabsorbent material.

BACKGROUND OF THE INVENTION

Cellulose fibers derived from wood pulp are used in a variety ofabsorbent articles, for example, diapers, incontinence products, andfeminine hygiene products. It is desirable for the absorbent articles tohave a high absorbent capacity for liquid, rapid liquid acquisition, lowrewet, as well as to have good dry and wet strength characteristics fordurability in use and effective fluid management. The absorbent capacityof articles made from cellulose fibers is often enhanced by the additionof absorbent materials, such as superabsorbent polymers. Superabsorbentpolymers known in the art have the capability to absorb liquids inquantities from 5 to 100 times or more their weight. Thus, the presenceof superabsorbent polymers greatly increases the liquid holding capacityof absorbent articles made from cellulose.

Because superabsorbent polymers absorb liquid and swell upon contactwith liquid, superabsorbent polymers have heretofore been incorporatedprimarily in cellulose mats that are produced by the conventional dry,air-laid methods. Wet-laid processes for forming cellulose mats have notbeen used commercially because superabsorbent polymers tend to absorbliquid and swell during formation of the absorbent mats, thus requiringsignificant energy for their complete drying.

Cellulose structures formed by the wet-laid process typically exhibitcertain properties that are superior to those of an air-laid structure.The integrity, fluid distribution, and the wicking characteristics ofwet-laid cellulosic structures are typically superior to those ofair-laid structures. Attempts to combine the advantages of wet-laidcomposites with the high absorbent capacity of superabsorbent materialshas led to the formation of various wet-laid absorbent composites thatinclude superabsorbent polymers. These structures can be generallycharacterized as structures that either have superabsorbent polymersdistributed on the surface of a wet-laid composite, laminates, or,alternatively, structures that have superabsorbent material distributedrelatively uniformly throughout the composite.

However, absorbent composites that contain superabsorbent materialscommonly suffer from gel blocking. Upon liquid absorption,superabsorbent materials tend to coalesce and form a gelatinous masswhich prevents the wicking of liquid to unwetted portions of thecomposite. By preventing distribution of acquired liquid from acomposite's unwetted portions, gel blocking precludes the effective andefficient use of superabsorbent materials in fibrous composites. Thewicking capacity of conventional fibrous composites that includerelatively homogeneous distributions of superabsorbent material isgenerally significantly restricted after initial liquid insult. Thediminished capacity of such fibrous composites results from narrowing ofcapillary acquisition and distribution channels that accompaniessuperabsorbent material swelling. The diminution of absorbent capacityand concomitant loss of capillary distribution channels for conventionalabsorbent cores that include superabsorbent material is manifested bydecreased liquid acquisition rates and far from ideal liquiddistribution on successive liquid insults.

Accordingly, there exists a need for an absorbent composite thatincludes superabsorbent material and that effectively acquires and wicksliquid throughout the composite and distributes the acquired liquid toabsorbent material where the liquid is efficiently absorbed and retainedwithout gel blocking. A need also exists for an absorbent composite thatcontinues to acquire and distribute liquid throughout the composite onsuccessive liquid insults. In addition, there exists a need for anabsorbent composition containing superabsorbent materials that exhibitsthe advantages associated with wet-laid composites including wetstrength, absorbent capacity and acquisition, liquid distribution,softness, and resilience. The present invention seeks to fulfill theseneeds and provides further related advantages.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides an absorbent fibrouscomposite containing absorbent material dispersed through the compositeand along the composite's length. On wetting, liquid acquired by thecomposite is distributed throughout the composite and ultimatelyabsorbed by the composite's absorbent material. In one embodiment, theabsorbent material is dispersed along the composite's length in bands.For such an embodiment, the absorbent material swells with acquiredliquid and the portion of the composite that includes absorbent materialexpands and raises from the composite's wetted surface to form ridges orflutes. The wetted composite's fluted structure enhances liquid wicking,acquisition, and distribution on subsequent liquid insult.

In another aspect of the present invention, absorbent articles thatinclude the fluted composite are provided. The absorbent articlesinclude consumer absorbent products such as diapers, feminine careproducts, and adult incontinence products.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a top view of a representative composite formed in accordancewith the present invention;

FIG. 2A is a cross-sectional view of a representative composite of thepresent invention in a dry state;

FIG. 2B is a cross-sectional view of a representative composite of thepresent invention in a wetted state;

FIG. 2C is a perspective view of the wetted composite shown in FIG. 2B;

FIG. 3 is a cross-sectional view of a representative composite formed inaccordance with the present invention;

FIG. 4A is a perspective view of the upper surface of a representativecomposite formed in accordance with the present invention;

FIG. 4B is a perspective view of the lower surface of a representativecomposite formed in accordance with the present invention;

FIG. 5 is a perspective view of a representative absorbent materialbanding pattern formed in accordance with the present invention;

FIG. 6 is a perspective view of another representative absorbentmaterial banding pattern formed in accordance with the presentinvention;

FIG. 7 is a perspective view of another representative absorbentmaterial banding pattern formed in accordance with the presentinvention;

FIG. 8 is a photomicrograph (15× magnification) of a portion of arepresentative composite formed in accordance with the presentinvention, the photomicrograph shows a machine direction view of across-machine direction cut through a region enriched with absorbentmaterial;

FIG. 9 is a photomicrograph (15× magnification) of a portion of arepresentative composite formed in accordance with the presentinvention, the photomicrograph shows a machine direction view of across-machine direction cut through a liquid distribution zone;

FIG. 10 is a photomicrograph (15× magnification) of a portion of arepresentative composite formed in accordance with the presentinvention, the photomicrograph shows a machine direction view of across-machine direction cut through an interface region of the compositebetween a liquid distribution zone and a region enriched with absorbentmaterial;

FIG. 11A is a perspective view of another representative compositeformed in accordance with the present invention;

FIG. 11B is a perspective view of an absorbent construct composed of thecomposite shown in FIG. 11A and an acquisition layer;

FIG. 12A is a diagrammatic view illustrating a device and method forforming the composite of the present invention;

FIG. 12B is a top plan view of a portion of a device for forming thecomposite of the present invention;

FIG. 13 is a diagrammatic view illustrating a twin-wire device andmethod for forming the composite of the present invention;

FIGS. 14A-14H are cross-sectional views of representative compositesformed in accordance with the present invention;

FIG. 15 is a diagrammatic view illustrating a representative headboxassembly and method for forming the composite of the present invention;

FIG. 16 is a diagrammatic view illustrating a representative headboxassembly and method for forming the composite of the present invention;

FIG. 17 is a view illustrating representative conduits for introducingabsorbent material into a fibrous web in accordance with the presentinvention;

FIG. 18 is a cross-sectional view of a portion of a component of anabsorbent article incorporating a representative composite formed inaccordance with the present invention;

FIG. 19 is a cross-sectional view of a portion of a component of anabsorbent article incorporating a representative composite formed inaccordance with the present invention;

FIG. 20 is a cross-sectional view of a portion of an absorbent constructincorporating a storage layer and a representative composite formed inaccordance with the present invention;

FIG. 21 is a cross-sectional view of a portion of an absorbent constructincorporating a storage layer and a representative composite formed inaccordance with the present invention;

FIG. 22 is a cross-sectional view of a portion of an absorbent constructincorporating a storage layer, an acquisition layer, and arepresentative composite formed in accordance with the presentinvention;

FIG. 23 is a cross-sectional view of a portion of an absorbent constructincorporating a storage layer, an acquisition layer, and arepresentative composite formed in accordance with the presentinvention;

FIGS. 24A-24D are cross-sectional views of a portion of absorbentconstructs incorporating a representative composite formed in accordancewith the present invention;

FIGS. 25A-25H are cross-sectional views of a portion of absorbentarticles incorporating a representative composite formed in accordancewith the present invention;

FIG. 26A is a cross-sectional view of a portion of an absorbent articleincorporating a representative composite formed in accordance with thepresent invention;

FIG. 26B is a cross-sectional view of a preferred embodiment of anabsorbent article incorporating a liquid pervious facing sheet, a liquidimpervious backing sheet, and a representative composite formed inaccordance with the present invention;

FIG. 27 is a cross-sectional view of a portion of an absorbent articleincorporating a representative composite formed in accordance with thepresent invention;

FIG. 28 is a cross-sectional view of a portion of an absorbent articleincorporating a representative composite formed in accordance with thepresent invention; and

FIG. 29 is a cross-sectional view of a portion of an absorbent articleincorporating a representative composite formed in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The absorbent composite of the present invention is a fibrous compositethat includes absorbent material. The absorbent composite includes afibrous matrix having absorbent material dispersed in bands along thecomposite's length. Between the composite's bands of absorbent materiallie distribution zones composed primarily of fibers. Generally, theabsorbent material serves to absorb and retain liquid acquired by thecomposite. The composite's fibrous distribution zones serve to acquireliquid contacting the composite and to distribute the acquired liquidthroughout the composite and, ultimately, to the absorbent material.

The absorbent composite can be advantageously incorporated into avariety of absorbent articles such as diapers including disposablediapers and training pants; feminine care products including sanitarynapkins, and pant liners; adult incontinence products; toweling;surgical and dental sponges; bandages; food tray pads; and the like.Because the composite is highly absorbent, the composite can be includedinto an absorbent article as a liquid storage core. In such a construct,the composite can be combined with one or more other composites orlayers including, for example, an acquisition and/or a distributionlayer. Alternatively, because the composite can rapidly acquire,distribute, and store liquid, the composite can be effectivelyincorporated into an absorbent article as the sole absorbent componentwithout including other individual layers such as acquisition and/ordistribution layers. In a preferred embodiment, the present inventionprovides an absorbent article, such as a diaper, that includes a flutedabsorbent composite having a liquid pervious facing sheet and a liquidimpervious backing sheet. In addition, because of the composite'scapacity to rapidly acquire and distribute liquid, the composite canserve as a liquid management layer that acquires and transfers a portionof the acquired liquid to an underlying storage core. Thus, in anotherembodiment, the absorbent composite can be combined with a storage coreto provide an absorbent core that is useful in absorbent articles.

The absorbent composite of the present invention is a fluted storagecomposite. As used herein, the term “fluted” refers to the nature of thecomposite, which on wetting, develops ridges or flutes as a result ofabsorbent material expansion. As noted above, absorbent material islocated in bands or stripes positioned across the composite's width andextending in bands along the composite's length. On contact with liquidacquired by the fibrous composite, absorbent material swelling occursand produces a wetted composite having ridges or flutes that includeswollen absorbent material separated by distribution zones or channels,regions of the composite that are generally substantially free ofabsorbent material.

The fluted composite of the present invention is a fibrous structureprepared from cellulosic fibers that have been wetted during theformation process and, as a result, provide a fibrous composite in whichthe fibers are bonded. As used in this context, the term “bonded” refersto hydrogen bonding that occurs between fibers that have been wetted andthen formed into a mat or web. The bonding that occurs between wettedfibers subsequently formed into a fibrous web results in a web that hasincreased strength and structural integrity, when both wet and dry,compared to air-laid webs. Fibrous webs formed from wetted fibers havestrength and integrity significantly greater than air-laid fibrous websformed from dry fibers, which are incapable of any significantinterfiber bonding. The mere proximity of dry fibers in a fibrous web isinsufficient to provide any significant bonding between fibers.Consequently, as is well know, air-laid fibrous webs generally lack wetor dry strength. In addition to standard wet-laid processes, wettedfibers can be produced and formed into fibrous webs by foam-formingprocesses.

The banded nature of the fluted absorbent composite of the presentinvention is illustrated in FIGS. 1-3. Referring to FIG. 1, arepresentative fluted absorbent composite indicated generally byreference 10 formed in accordance with the present invention includesregions 12 enriched with absorbent material (i.e., liquid storage zones)and fibrous regions 14 that are substantially free of absorbent material(i.e., liquid distribution zones). Regions 12 enriched- with absorbentmaterial are generally fibrous regions to which have been addedabsorbent material.

When the absorbent composite is contacted with liquid, liquid is rapidlyacquired by the predominantly fibrous regions of the composite. Thefibrous regions are relatively open and porous in nature and promoterapid liquid acquisition, wicking, and distribution. Liquid acquired bythe composite generally travels rapidly longitudinally through thefibrous composite along the composite's length via the distributionzones (i.e., regions 14) and is absorbed by regions of the compositeenriched with absorbent material (i.e., regions 12). The acquired liquidis generally wicked laterally into the absorbent material as the liquidis distributed along the composite's length.

For the fluted composite, successive liquid insults are absorbed at arate greater than the rate for initial insult through the establishmentof flutes and channels on initial liquid insult. On wetting, thecomposite of the present invention becomes a fluted structure havingchannels for rapidly acquiring additional liquid and distributing theliquid to sites that are remote to insult. Uptake of liquid bysuperabsorbent leads to expansion and enhancement of voids in thefibrous structure. For the fluted composite, acquisition times forsubsequent liquid insult are generally less than that for the initialacquisition. Reduced acquisition times for successive liquid insults isnot generally observed for conventional absorbent constructs. Becauseconventional absorbent structures cannot form a fluted structure andtherefore lack channels for distributing additional liquid, acquisitiontimes for these structures generally increase for successive liquidinsults. Increased acquisition time is attributable to the fact thatliquid is only slowly acquired and distributed through a composite'ssaturated regions to more remote regions of the composite that arecapable of absorbing liquid. Thus, the fluted absorbent compositeprovides for initial liquid acquisition rates that are generallycomparable or greater than for conventional absorbent structures andhave significantly increased rates of liquid acquisition for successiveliquid acquisition relative to conventional composites.

The dry and wet structures of the fluted composite of the presentinvention are illustrated in FIGS. 2A and 2B, which are lateralcross-sectional views of a representative fluted absorbent composite.FIG. 2A is a cross-sectional view of the dry composite shown in FIG. 1indicating regions 12 and 14 and the relatively uniform thickness of theunwetted composite. FIG. 2B is a cross-sectional view of the compositeshown in FIG. 1 in a wetted state, for example, after liquid insult andliquid absorption and swelling and expansion of the absorbent material.Referring to FIG. 2B, absorbent material enriched regions 12 (i.e.,liquid storage regions) are shown as ridges or flutes separated byfibrous regions 14 (i.e., liquid distribution zones) that form a valleyfloor or channel between the flutes. Due at least in part to the flutedstructure of the wetted fibrous composite, subsequent liquid insults arerapidly absorbed by the fluted composite compared to compositescontaining absorbent material in other configurations, for example,composites in which the absorbent material is distributed substantiallyuniformly throughout the composite and that are particularly susceptibleto gel blocking, low acquisition rates, and liquid leakage.

Liquid acquisition rates and times for a representative fluted absorbentcomposite are compared to those of storage cores having relativelyuniform distributions of absorbent material in Example 1. Acquisitionrates for the fluted absorbent composite were significantly greater thanfor commercially available cores which showed acquisition rates thatdecreased substantially with successive insults. In contrast, thecomposite of the invention maintained high rates for three insults. Thefluted composite also exhibited rates greater than for a similarlycomposed wet composite having a relatively uniform distribution ofabsorbent material throughout the composite.

Example 2 compares the wicking characteristics of a representativefluted absorbent composite to a commercially available diaper core and awet-laid fibrous core that contains superabsorbent material distributedsubstantially uniformly throughout the composite. The horizontal andvertical wicking results indicate that the air-laid commercial core hasthe poorest wicking characteristics, while the fluted composite of theinvention having bands of absorbent material exhibits significantlyenhanced wicking compared to a similarly composed composite thatincludes relatively uniformly distributed absorbent material.

Distribution of liquid from the site of insult throughout the compositedemonstrates the composite's wicking capacity and efficiency of materialutilization. The liquid distribution of a representative flutedcomposite is compared to two commercially available diaper cores inExample 3. The results indicate that, in contrast to the commercialcores which suffer from liquid accumulation at the site of insult, thefluted composite has nearly ideal distribution, distributing liquidthroughout the entire composite and fully utilizing the composite'smaterials.

Because liquid insults are absorbed in a conventional storage core at arate less than the average infant's urination rate, liquid can leak fromthe diaper at its edges. To prevent such leakage, diaper manufacturershave developed elaborate and expensive leg cuff gasketing systems thatfit tightly about an infant's leg and is generally uncomfortable andleaves marks. When incorporated into a diaper as a storage core, thefluted composite of this invention overcome the problems of edge leakingassociated with conventional storage cores. Accordingly, in onepreferred embodiment, the fluted absorbent composite includes outermostbands of absorbent material that include relatively greater amounts ofabsorbent than the inner bands. Referring to FIG. 3, outermost absorbentmaterial enriched regions 12 have a greater amount of absorbent materialrelative to the inner regions 12 and, as a consequence, have a greaterabsorbent capacity and therefore can swell and expand to greater sizethat those flutes containing relatively lesser amount of absorbentmaterial. The fluted absorbent core having relatively greater amount ofabsorbent material in the outermost regions 12 can assist in theprevention of liquid leaking from the edge of the composite. In anotherpreferred embodiment, outermost absorbent materials enriched regions 12contain absorbent material having a higher absorptive and/or liquidretention capacity than the absorbent material contained in innerregions 12.

An infant's skin is always susceptible to irritation and rash resultingfrom moisture associated with retained liquid from a diaper's storagecore. The amount of liquid released from an absorbent article that hasacquired liquid is referred to as “rewet”. While a storage core'ssurface is generally necessarily hydrophilic to effectively absorbliquid, such hydrophilic surfaces also promote rewet. In contrast toconventional absorbent articles that are in continuous contact with awearer's skin, the fluted composite's surface contacts the wearer onlyat the flute's ridgetops thereby minimizing contact with the wearer'sskin and rewet. Because of the minimized contact between an infant'sskin and the wetted surface of the fluted absorbent composite of thepresent invention compared to the wetted surface of a conventionalstorage core, the fluted absorbent composite offers advantages relatingto skin health and comfort to the wearer. It is contemplated that thecomposite's fluted structure also provides skin health advantagesrelated to cooling and air flow through an absorbent article thatcontains the fluted composite. The rewet performance of a representativefluted absorbent composite is compared to a commercially availablediaper core in Example 1. Generally, for successive insults, rewetincreases for the commercial core. In contrast, rewet remains low andsubstantially unchanged for the fluted composite of this invention.

The structure of fluted composite offers the possibility of furtherreduction in rewet. Liquid insult generally occurs across the width ofthe composite which includes bands of fibrous regions and regionsenriched with absorbent material. Liquid is generally rapidly acquiredand distributed through the composite's fibrous regions (i.e., regions14) and generally stored in the composite's regions enriched withabsorbent material (i.e., regions 12). Ultimately, the acquired liquidresides in the bands of absorbent material in the fluted structure. Tofurther reduce rewet, the fluted absorbent composite can include ahydrophobic barrier coincident with the top surface of the composite'sflutes (i.e., coatings for the surfaces of regions 12). Suitablehydrophobic barriers generally include latex and other hydrophobic filmsand coatings known in the art. Because the distribution zones betweenthe coated flutes (i.e., regions 14) are physically removed from thewearer and because the wearer is protected from the flutes containingthe absorbent material and acquired liquid by a hydrophobic barrier,such a coated fluted composite provides for increased skin healththrough a reduction of skin wetness. Optionally, a hydrophobic barriercan also be affixed to the outward facing surface of the absorbentcomposite. Such a construction allows for a reduction in the thicknessof the polyethylene moisture barrier (i.e., liquid impervious backingsheet) traditionally employed in a diaper. The application of ahydrophobic barrier to the outward surface of the composite would reducetotal cost and material usage in an absorbent article incorporating thefluted absorbent composite.

A representative fluted absorbent composite having a hydrophobic barriercoincident with the composite's bands of absorbent material and affixedto inward surface of the composite is illustrated in FIG. 4A. Referringto FIG. 4A, coated composite 20 includes regions 12 and 14, as describedabove, and hydrophobic barriers 16 substantially coincident with andcovering regions 12 enriched with absorbent material. A representativefluted absorbent composite having a hydrophobic barrier affixed to theoutward facing surface of a fluted absorbent composite is illustrated inFIG. 4B.

Fibers are a principal component of the fluted absorbent composite ofthis invention. Fibers suitable for use in the present invention areknown to those skilled in the art and include any fiber from which anabsorbent composite can be formed. Suitable fibers include natural andsynthetic fibers. Combinations of fibers including combinations ofsynthetic and natural fibers, and treated and untreated fibers, can alsobe suitably used in the composite.

Generally, fibers are present in the composite in an amount from about20 to about 90 weight percent, preferably from about 50 to about 70weight percent, based on the total weight of the composite. In apreferred embodiment, the composite includes about 60 percent by weightfibers.

The composite of the invention includes resilient fibers. As usedherein, the term “resilient fiber” refers to a fiber present in thecomposite that imparts reticulation to the composite. Generally,resilient fibers provide the composite with bulk and resiliency. Theincorporation of resilient fibers into the composite allows thecomposite to expand on absorption of liquid without structural integrityloss. Resilient fibers also impart softness to the composite. Inaddition, resilient fibers offer advantages in the composite's formationprocesses. Because of the porous and open structure resulting from wetcomposites that include resilient fibers, these composites drain waterrelatively easily and are therefore dewatered and dried more readilythan wet composites that do not include resilient fibers. Preferably,the composite includes resilient fibers in an amount from about 10 toabout 60 percent by weight, more preferably from about 20 to 50 percentby weight, based on the total weight of the composite.

Resilient fibers include cellulosic and synthetic fibers. Preferredresilient fibers include chemically stiffened fibers, anfractuousfibers, chemithermomechanical pulp (CTMP), and prehydrolyzed kraft pulp(PHKP).

The term “chemically stiffened fiber” refers to a fiber that has beenstiffened by chemical means to increase fiber stiffness under dry andwet conditions. Fibers can be stiffened by the addition of chemicalstiffening agents that can coat and/or impregnate the fibers. Stiffeningagents include the polymeric wet strength agents including resinousagents such as, for example, polyamide-epichlorohydrin andpolyacrylamide resins described below. Fibers can also be stiffened bymodifying fiber structure by, for example, chemical crosslinking.Preferably, the chemically stiffened fibers are intrafiber crosslinkedcellulosic fibers.

Resilient fibers can include noncellulosic fibers including, forexample, synthetic fibers such as polyolefin, polyamide, and polyesterfibers. In a preferred embodiment, the resilient fibers includecrosslinked cellulosic fibers.

As used herein, the term “anfractuous fiber” refers to a cellulosicfiber that has been chemically treated. Anfractuous fibers include, forexample, fibers that have been treated with ammonia.

In addition to resilient fibers, the composite of the invention includesmatrix fibers. As used herein, the term “matrix fiber” refers to a fiberthat is capable of forming hydrogen bonds with other fibers. Matrixfibers are included in the composite to impart strength to thecomposite. Matrix fibers include cellulosic fibers such as wood pulpfibers, highly refined cellulosic fibers, and high surface area fiberssuch as expanded cellulose fibers. Other suitable cellulosic fibersinclude cotton linters, cotton fibers, and hemp fibers, among others.Preferably, the composite includes matrix fibers in an amount from about10 to about 50 percent by weight, more preferably from about 15 to about30 percent by weight, based on the total weight of the composite.

The composite of the present invention preferably includes a combinationof resilient and matrix fibers. In one preferred embodiment, thecomposite includes resilient fibers in an amount from about 25 to about50 percent by weight and matrix fibers in an amount from about 10 toabout 40 percent by weight based on the total weight of the composite.In a more preferred embodiment, the composite includes from about 30 toabout 45 percent by weight resilient fibers, preferably crosslinkedcellulosic fibers, and from about 15 to about 30 percent by weightmatrix fibers, preferably wood pulp fibers, based on the total weight offibers in the composite. For representative composites formed bywet-laid and foam processes, the composite preferably includes about 45percent by weight resilient fibers (e.g., crosslinked cellulosic fibers)and about 15 percent by weight matrix fibers.

Cellulosic fibers can be a basic component of the fluted absorbentcomposite. Although available from other sources, cellulosic fibers arederived primarily from wood pulp. Suitable wood pulp fibers for use withthe invention can be obtained from well-known chemical processes such asthe kraft and sulfite processes, with or without subsequent bleaching.Pulp fibers can also be processed by thermomechanical,chemithermomechanical methods, or combinations thereof. The preferredpulp fiber is produced by chemical methods. Ground wood fibers, recycledor secondary wood pulp fibers, and bleached and unbleached wood pulpfibers can be used. Softwoods and hardwoods can be used. Details of theselection of wood pulp fibers are well-known to those skilled in theart. These fibers are commercially available from a number of companies,including Weyerhaeuser Company, the assignee of the present invention.For example, suitable cellulose fibers produced from southern pine thatare usable with the present invention are available from WeyerhaeuserCompany under the designations CF416, NF405, PL416, FR516, and NB416.

The wood pulp fibers of the present invention can also be pretreatedprior to use with the present invention. This pretreatment may includephysical treatment, such as subjecting the fibers to steam, or chemicaltreatment, for example, crosslinking the cellulose fibers using any oneof a variety of crosslinking agents. Crosslinking increases fiber bulkand resiliency, and thereby can improve the fibers' absorbency.Generally, crosslinked fibers are twisted or crimped. The use ofcrosslinked fibers allows the composite to be more resilient, softer,bulkier, and to have enhanced wicking. Suitable crosslinked cellulosefibers produced from southern pine are available from WeyerhaeuserCompany under the designation NBH416. Crosslinked cellulose fibers andmethods for their preparation are disclosed in U.S. Pat. Nos. 5,437,418and 5,225,047 issued to Graef et al., expressly incorporated herein byreference.

Crosslinked fibers can be prepared by treating fibers with acrosslinking agent. Suitable cellulose crosslinking agents includealdehyde and urea-based formaldehyde addition products. See, forexample, U.S. Pat. Nos. 3,224,926; 3,241,533; 3,932,209; 4,035,147;3,756,913; 4,689,118; 4,822,453; U.S. Pat. No. 3,440,135, issued toChung; U.S. Pat. No. 4,935,022, issued to Lash et al.; U.S. Pat. No.4,889,595, issued to Herron et al.; U.S. Pat. No. 3,819,470, issued toShaw et al.; U.S. Pat. No. 3,658,613, issued to Steiger et al.; and U.S.Pat. No. 4,853,086, issued to Graef et al., all of which are expresslyincorporated herein by reference in their entirety. Cellulose fibershave also been crosslinked by carboxylic acid crosslinking agentsincluding polycarboxylic acids. U.S. Pat. Nos. 5,137,537; 5,183,707; and5,190,563, describe the use of C2-C9 polycarboxylic acids that containat least three carboxyl groups (e.g., citric acid and oxydisuccinicacid) as crosslinking agents.

Suitable urea-based crosslinking agents include methylolated ureas,methylolated cyclic ureas, methylolated lower alkyl substituted cyclicureas, methylolated dihydroxy cyclic ureas, dihydroxy cyclic ureas, andlower alkyl substituted cyclic ureas. Specific preferred urea-basedcrosslinking agents include dimethylol urea (DMU,bis[N-hydroxymethyl]urea), dimethylolethylene urea (DMEU,1,3-dihydroxymethyl-2-imidazolidinone), dimethyloldihydroxyethylene urea(DMDHEU, 1,3-dihydroxymethyl-4,5-dihydroxy-2-imidazolidinone),dimethyl-dihydroxy urea (DMDHU), dihydroxyethylene urea (DHEU,4,5-dihydroxy-2-imidazolidinone), and dimethyldihydroxyethylene urea(DMeDHEU, 4,5-dihydroxy-1,3-dimethyl-2-imidazolidinone).

Suitable polycarboxylic acid crosslinking agents include citric acid,tartaric acid, malic acid, succinic acid, glutaric acid, citraconicacid, itaconic acid, tartrate monosuccinic acid, and maleic acid. Otherpolycarboxylic acids crosslinking agents include polymericpolycarboxylic acids such as poly(acrylic acid), poly(methacrylic acid),poly(maleic acid), poly(methylvinylether-co-maleate) copolymer,poly(methyl-vinylether-co-itaconate) copolymer, copolymers of acrylicacid, and copolymers of maleic acid. The use of polymeric polycarboxylicacid crosslinking agents such as polyacrylic acid polymers, polymaleicacid polymers, copolymers of acrylic acid, and copolymers of maleic acidis described in U.S. patent application Ser. No. 08/989,697, filed Dec.12, 1997, and assigned to Weyerhaeuser Company. Mixtures or blends ofcrosslinking agents may also be used.

The crosslinking agent can include a catalyst to accelerate the bondingreaction between the crosslinking agent and cellulose fiber. Suitablecatalysts include acidic salts, such as ammonium chloride, ammoniumsulfate, aluminum chloride, magnesium chloride, and alkali metal saltsof phosphorous-containing acids.

Although not to be construed as a limitation, examples of pretreatingfibers include the application of surfactants or other liquids whichmodify the surface chemistry of the fibers. Other pretreatments includeincorporation of antimicrobials, pigments, dyes and densification orsoftening agents. Fibers pretreated with other chemicals, such asthermoplastic and thermosetting resins also may be used. Combinations ofpretreatments also may be employed. Similar treatments can also beapplied after the composite formation in post-treatment processes.

Cellulosic fibers treated with particle binders and/ordensification/softness aids known in the art can also be employed inaccordance with the present invention. The particle binders serve toattach other materials, such as cellulosic fiber superabsorbentpolymers, as well as others, to the cellulosic fibers. Cellulosic fiberstreated with suitable particle binders and/or densification/softnessaids and the process for combining them with cellulose fibers aredisclosed in the following U.S. patents: (1) U.S. Pat. No. 5,543,215,entitled “Polymeric Binders for Binding Particles to Fibers”; (2) U.S.Pat. No.5,538,783, entitled “Non-Polymeric Organic Binders for BindingParticles to Fibers”; (3) U.S. Pat. No. 5,300,192, entitled “Wet LaidFiber Sheet Manufacturing With Reactivatable Binders for BindingParticles to Binders”; (4) U.S. Pat. No. 5,352,480, entitled “Method forBinding Particles to Fibers Using Reactivatable Binders”; (5) U.S. Pat.No. 5,308,896, entitled “Particle Binders for High-Bulk Fibers”; (6)U.S. Pat. No. 5,589,256, entitled “Particle Binders that Enhance FiberDensification”; (7) U.S. Pat. No. 5,672,418, entitled “ParticleBinders”; (8) U.S. Pat. No. 5,607,759, entitled “Particle Binding toFibers”; (9) U.S. Pat. No. 5,693,411, entitled “Binders for BindingWater Soluble Particles to Fibers”; (10) U.S. Pat. No. 5,547,745.,entitled “Particle Binders”; (11) U.S. Pat. No. 5,641,561, entitled“Particle Binding to Fibers”; (12) U.S. Pat. No. 5,308,896, entitled“Particle Binders for High-Bulk Fibers”; (13) U.S. Pat. No. 5,498,478,entitled “Polyethylene Glycol as a Binder Material for Fibers”; (14)U.S. Pat. No. 5,609,727, entitled “Fibrous Product for BindingParticles”; (15) U.S. Pat. No. 5,571,618, entitled “ReactivatableBinders for Binding Particles to Fibers”; (16) U.S. Pat. No. 5,447,977,entitled “Particle Binders for High Bulk Fibers”; (17) U.S. Pat. No.5,614,570, entitled “Absorbent Articles. Containing Binder Carrying HighBulk Fibers; (18) U.S. Pat. No. 5,789,326, entitled “Binder TreatedFibers”; and (19) U.S. Pat. No. 5,611,885, entitled “Particle Binders”;all expressly incorporated herein by reference.

In addition to natural fibers, synthetic fibers including polymericfibers, such as polyolefin, polyamide, polyester, polyvinyl alcohol,polyvinyl acetate fibers, and can also be used in the absorbentcomposite of the present invention. Suitable synthetic fibers include,for example, polyethylene terephthalate, polyethylene, polypropylene,nylon, and rayon fibers. Other suitable synthetic fibers include thosemade from thermoplastic polymers, cellulosic and other fibers coatedwith thermoplastic polymers, and multicomponent fibers in which at leastone of the components includes a thermoplastic polymer. Single andmulticomponent fibers can be manufactured from polyester, polyethylene,polypropylene, and other conventional thermoplastic fibrous materials.Single and multicomponent fibers are commercially available. Suitablebicomponent fibers include Celbond® fibers available fromHoechst-Celanese Company. The absorbent composite can also includecombinations of natural and synthetic fibers. Synthetic fibers,including blends of natural and synthetic fibers, can be utilized in thecomposite's flutes and/or distribution zones.

In one preferred embodiment, the absorbent composite includes acombination of pulp fibers (e.g., Weyerhaeuser designation NB416) andcrosslinked cellulosic fibers (e.g., Weyerhaeuser designation NHB416).In a preferred embodiment, the absorbent composite includes acombination of pulp fibers present in the composite in about 50 weightpercent and crosslinked cellulosic fibers present in the composite inabout 50 weight percent based on the total weight of fibers.

In a preferred embodiment, the wet-laid or foam-formed fluted compositeis formed from a fiber furnish that includes a blend of refined southernpine fibers and crosslinked fibers. Composites formed from such a blendhave increased sheet integrity and enhanced bulk compared to compositesformed from a mixture of southern pine and crosslinked fibers that hasbeen refined. Optionally, the blend of refined southern pine fibers andcrosslinked fibers can be further lightly refined.

The fluted absorbent composite of the present invention can serve as astorage layer for acquired liquids when incorporated into an absorbentarticle. To effectively retain acquired liquids, the composite includesabsorbent material.

As described above, absorbent material is located in bands incorporatedinto the fibrous composite. Basically, bands of absorbent material canbe configured in virtually any shape, size, and composite location.Suitable configurations of the composite's bands include anyconfiguration that does not impede liquid acquisition or promote gelblocking. The bands of absorbent material can include straight andparallel bands, curved or wavy bands, and zigzag bands, among others. Arepresentative banded absorbent composite having wavy bands isillustrated in FIG. 5. The composite's bands can also include pulsedbands of absorbent material. As used herein the term “pulsed band”refers to a band that extends along the composite's length that is not acontinuous band, but rather is a band that is interrupted by regionscontaining substantially no absorbent material. A function of the pulsedbands is to provide the composite with enhanced liquid distributioncapacity across the composite's width (i.e., the cross-machinedirection). A representative banded absorbent composite having pulsedbands is illustrated in FIG. 6. As illustrated in FIG. 6, in oneembodiment, the pulsed bands have an offset configuration to furtherenhance cross-machine direction liquid distribution. Such an offsetconfiguration of absorbent material can be formed by injecting absorbentmaterial into the composite through nozzles delivering nonsynchronouspulses of absorbent material (i.e., pulses from one nozzle that is notsynchronized with pulses from another nozzle). The length of the pulsedband can vary greatly and can, for example, be a dot or spot ofabsorbent material having a length equal to about its width. Arepresentative banded absorbent composite having pulsed bands resemblingdots or spots is illustrated in FIG. 7.

The composite's bands or flutes are regions of the composite that areenriched with absorbent material. The composite's distribution zones caninclude some absorbent material. It will be appreciated that whileabsorbent material is incorporated into the composite in bands, theformation of absorbent material bands in the composite can lead to theintroduction of some absorbent material into the composite's fibrousdistribution zones. The incorporation of absorbent material into thecomposite can result in some mixing between the absorbent material afibers present in the fibrous base. The result is a transition zonebetween the primarily fibrous distribution zones and the absorbentmaterial bands. Such a transition zone includes both fibers andabsorbent material. The composite's fibrous matrix can also be formed toinclude some absorbent materials thereby resulting in distribution zonescontaining absorbent material. In embodiments having absorbent materialin the distribution zones, the amount of absorbent material present isnot so great as to diminish the effectiveness of these zones indistributing acquired liquid.

Cross-sectional views of a representative composite formed by a wet-laidmethod are shown in the photomicrographs in FIGS. 8-10. FIG. 8 is amachine direction view of a cross-machine direction cut through thecomposite's absorbent material band (i.e., region 12 of the compositeenriched with absorbent material). FIG. 9 is a machine direction view ofa cross-machine direction cut through a distribution zone (i.e., region14 of the composite substantially free of absorbent material). FIG. 10is a machine direction view of a cross-machine direction cut through thecomposite intermediate an absorbent material band and a distributionzone (i.e., through a transition zone as described above).

As use herein, the term “absorbent material” refers to a material thatabsorbs liquid and that generally has an absorbent capacity greater thanthe cellulosic fibrous component of the composite. Preferably, theabsorbent material is a water swellable, generally water insolublepolymeric material capable of absorbing at least about 5, desirablyabout 20, and preferably about 100 times or more its weight in saline(e.g., 0.9 percent saline). The absorbent material can be swellable inthe dispersion medium utilized in the method for forming the composite.In one embodiment, the absorbent material is untreated and swellable inthe dispersion medium. In another embodiment, the absorbent material isan absorbent material that is resistant to absorbing water during thecomposite formation process. Such absorbent materials that are resistantto absorption include coated and chemically modified absorbentmaterials.

The amount of absorbent material present in the composite can varygreatly depending on the composite's intended use. When the absorbentcomposite is used as a stand alone absorbent composite as in, forexample, an absorbent toweling, the amount of absorbent material in thecomposite is comparative low (e.g., about 0.1 weight percent). Theamount of absorbent material present in an absorbent article such as anabsorbent core for an infant's diaper is considerably greater. In such aconstruct, the absorbent material is suitably present in the compositein an amount from about 10 to about 80 weight percent, preferably fromabout 30 to about 50 weight percent, based on the total weight of thecomposite. In preferred embodiments, the composite includes about 40percent by weight absorbent material based on the total weight of thecomposite.

The absorbent material may include natural materials such as agar,pectin, and guar gum, and synthetic materials, such as synthetichydrogel polymers. Synthetic hydrogel polymers include, for example,carboxymethyl cellulose, alkaline metal salts of polyacrylic acid,polyacrylamides, polyvinyl alcohol, ethylene maleic anhydridecopolymers, polyvinyl ethers, hydroxypropyl cellulose, polyvinylmorpholinone, polymers and copolymers of vinyl sulphonic acid,polyacrylates, polyacrylamides, and polyvinyl pyridine among others. Ina preferred embodiment, the absorbent material is a superabsorbentmaterial. As used herein, a “superabsorbent material” refers to apolymeric material that is capable of absorbing large quantities offluid by swelling and forming a hydrated gel (i.e., a hydrogel). Inaddition to absorbing large quantities of fluids, superabsorbentpolymers can also retain significant amounts of bodily fluids undermoderate pressure.

Superabsorbent polymers generally fall into three classes: starch graftcopolymers, crosslinked carboxymethylcellulose derivatives, and modifiedhydrophilic polyacrylates. Examples of such absorbent polymers includehydrolyzed starch-acrylonitrile graft copolymers, neutralizedstarch-acrylic acid graft copolymers, saponified acrylic acidester-vinyl acetate copolymers, hydrolyzed acrylonitrile copolymers oracrylamide copolymers, modified crosslinked polyvinyl alcohol,neutralized self-crosslinking polyacrylic acids, crosslinkedpolyacrylate salts, carboxylated cellulose, and neutralized crosslinkedisobutylene-maleic anhydride copolymers.

Superabsorbent polymers are available commercially, for example,polyacrylates from Clariant of Portsmouth, Va. These superabsorbentpolymers come in a variety of sizes, morphologies and absorbentproperties (available from Clariant under trade designations such as IM3500 and IM 3900). Other superabsorbent particles are marketed under thetrademarks SANWET (supplied by Sanyo Kasei Kogyo Kabushiki Kaisha), andSXM77 (supplied by Stockhausen of Greensboro, N.C.). Othersuperabsorbent polymers are described in U.S. Pat. No. 4,160,059; U.S.Pat. No. 4,676,784; U.S. Pat. No. 4,673,402; U.S. Pat. No. 5,002,814;U.S. Pat. No. 5,057,166; U.S. Pat. No. 4,102,340; and U.S. Pat. No.4,818,598, all expressly incorporated herein by reference. Products suchas diapers that incorporate superabsorbent polymers are described inU.S. Pat. No. 3,699,103 and U.S. Pat. No. 3,670,731.

Suitable superabsorbent polymers useful in the absorbent composite ofthe present invention include superabsorbent polymer particles andsuperabsorbent polymer fibers.

In a preferred embodiment, the absorbent composite of the presentinvention includes a superabsorbent material that that swells relativelyslowly for the purposes of composite manufacturing and yet swells at anacceptable rate so as not to adversely affect the absorbentcharacteristics of the composite or any construct containing thecomposite.

In one embodiment, the present invention provides a composite havingabsorbent material present in the composite in a concentration gradient.As used herein, the term “concentration gradient” refers to a gradientin the concentration of absorbent material in the fibrous composite withrespect to a particular dimension (i.e., thickness, width, and length)of the composite. An absorbent material concentration gradient is formedthrough selective distribution of the material into the composite. Forexample, as described below, introduction of the absorbent material intothe composite can be accomplished with significant fiber mixing and anaccompanying loss of an absorbent material concentration gradient.Alternatively, the absorbent material can be introduced into thecomposite without significant fiber mixing resulting in the formation ofa relatively greater concentration gradient. The composite'sconcentration gradient can be present in either the z-direction (i.e.,the thickness of the composite), the x-direction (i.e., across the widthof the composite, the cross-machine direction), the y-direction (i.e.,along the length of the composite, the machine direction) orcombinations of the x-, y- and z-directions. Concentration gradients ofabsorbent material are contemplated to increase liquid wicking andfurther to reduce the potential for gel blocking.

In another embodiment, the present invention provides a banded compositehaving absorbent material relatively uniformly distributed across itswidth and extending along its length throughout its thickness inaddition to absorbent material present in the bands. The absorbentmaterial is distributed into the fibrous composite as described belowand preferably is present in the composite in a concentration gradient.Preferably the concentration gradient is present in at least thez-direction (i.e., the composite's thickness), although gradients in thex- and y-directions are also contemplated to provide useful composites.Composites of the present invention include those having concentrationgradients in one or more of the x-, y-, and z-directions. Forembodiments having a z-direction gradient, the high concentrationsurface is preferably positioned in an absorbent article away fromliquid insult. In one embodiment having a concentration gradient in thex-direction (i.e., the composite's width), the concentration ispreferably maximal at center of the composite's width and decreasesoutwardly from the center toward the composite's edges. In anotherembodiment, the concentration is preferably maximal at the composite'sedges. Gradients in the y-direction generally provide regions ofabsorbent material along the composite's length.

The absorbent composite of this invention optionally includes a wetstrength agent. The wet strength agent provides increased strength tothe absorbent composite and enhances the composites wet integrity. Inaddition to increasing the composites wet strength, the wet strengthagent can assist in binding the absorbent material, for example,superabsorbent material, in the composite's fibrous matrix.

Suitable wet strength agents include cationic modified starch havingnitrogen-containing groups (e.g., amino groups) such as those availablefrom National Starch and Chemical Corp., Bridgewater, N.J.; latex; wetstrength resins such as polyamide-epichlorohydrin resin (e.g., Kymene®557LX, Hercules, Inc., Wilmington, Del.), polyacrylamide resin(described, for example, in U.S. Pat. No. 3,556,932 issued Jan. 19, 1971to Coscia et al.; also, for example, the commercially availablepolyacrylamide marketed by American Cyanamid Co., Stanford, Conn., underthe trade name Parez™ 631 N.C.); urea formaldehyde and melamineformaldehyde resins, and polyethylenimine resins. A general discussionon wet strength resins utilized in the paper field, and generallyapplicable in the present invention, can be found in TAPPI monographseries No. 29, “Wet Strength in Paper and Paperboard”, TechnicalAssociation of the Pulp and Paper Industry (New York, 1965).

Generally, the wet strength agent is present in the composition in anamount from about 0.01 to about 2 weight percent, preferably from about0.1 to about 1 weight percent, and more preferably from about 0.3 toabout 0.7 weight percent, based on the total weight of the composite. Ina preferred embodiment, the wet strength agent useful in the compositeof the present invention is a polyamide-epichlorohydrin resin such ascommercially available from Hercules, Inc. under the designationKymene®. The wet and dry tensile strength of an absorbent compositeformed in accordance with the present invention will generally increasewith an increasing the amount of wet strength agent.

It has been observed that after successive liquid insults, thecomposites formed in accordance with the present invention maintaintheir structural integrity and remain substantially intact on removalfrom a diaper construct. In contrast, conventional storage cores thatcontain superabsorbent material lose structural integrity in a wetteddiaper. Thus, the wet tensile strength of the fluted absorbent cores ofthe present invention significantly exceeds that of conventional storagecores.

The absorbent composite of the present invention generally has a basisweight from about 50 to about 1000 g/m², and preferably from about 200to about 800 g/m². In a more preferred embodiment, the absorbentcomposite has a basis weight from about 300 to about 600 g/m². The basisweight of the fluted composite can be varied and will depend on itsintended use. When the fluted composite's intended use is as a storagelayer, the composite preferably has a basis weight greater than about300 g/m². For use as a liquid management layer, the composite preferablyhas a basis weight from about 100 to about 400 g/m². The absorbentcomposite generally has an average density (in the cross-machinedirection) of from about 0.03 to about 0.8 g/cm³, preferably from about0.04 to about 0.3 g/cm³. In a more preferred embodiment, the absorbentcomposite has an average density of about 0.15 g/cm³.

In one embodiment, the absorbent composite is a densified composite.Densification methods useful in producing the densified composites ofthe present invention are well known to those in the art. See, forexample, U.S. Pat. No. 5,547,541 and patent application Ser. No.08/859,743, filed May 21, 1997, entitled “Softened Fibers and Methods ofSoftening Fibers,” assigned to Weyerhaeuser Company, both expresslyincorporated herein by reference. Post dryer densified absorbentcomposites of this invention generally have a density from about 0.1 toabout 0.5 g/cm³, and preferably about 0.15 g/cm³. Predryer densificationcan also be employed. Preferably, the absorbent composite is densifiedby either a heated or room temperature calender roll method. See, forexample, U.S. Pat. Nos. 5,252,275 and 5,324,575, both expresslyincorporated herein by reference.

The composition of the absorbent composite of the present invention canbe varied to suit the intended use of the end product in which thecomposite is incorporated. In one preferred embodiment, the absorbentcomposite of the present invention includes about 60 weight percentcellulosic fibers, about 40 percent by weight absorbent material (e.g.,superabsorbent polymeric particles), and about 0.25 percent by weightwet strength agent (e.g., polyamide-epichlorohydrin resin, Kymene®,about 2-20 pounds resin per ton fiber) based on the total weight of thecomposite.

The dimensions of the fluted absorbent composite of the presentinvention can be varied greatly depending on the desired characteristicsof the composite and its intended use. Typically, for a child's diaper,the composite includes from about 2 to about 6 bands of absorbentmaterial across the composite's width, the outward edges of thecomposite preferably including bands of absorbent material. For atypical adult incontinence product, the composite can include 10 or morebands. Although the configuration and widths of the bands are notparticularly critical, the bands of absorbent material are generallyevenly spaced across the composite's width and have widths of from about0.10 to about 0.75 inch. The bands are typically separated bydistribution zones having widths from about 0.10 to about 1.0 inch.Feminine care products contain a relatively low amount of absorbentmaterial and fluted composites useful in such products have relativelynarrow bands of absorbent material.

The fluted structure of the composite of the present invention can beformed by a variety of methods known to those in the art, all of whichare within the scope of this invention. For example, a fluted structurecan be formed by attaching one of more bands of absorbent material oracquisition/distribution material to a fibrous base; depositing,injecting, applying, impregnating, or infusing absorbent material into afibrous base; or by wet-laid and foam-forming processes as describedbelow.

For embodiments that are formed by attaching bands of absorbent oracquisition/distribution materials to a fibrous base, the bands canfurther include other materials such as fibers. For these embodiments,the absorbent material-containing bands and the fibrous base can beindependently formed by methods known to those in the art includingair-laid, wet-laid, and foam-forming methods, as described below. Thefluted composite can be formed by affixing or attaching the bands to afibrous base by any method that permits fluid communication betweenthese components of the composite. Suitable means for affixing orattaching include, for example, gluing, thermobonding, and entangling.Generally, these embodiments have improved absorbent properties due toenhanced fluid communication between the composite's components comparedto the composites that have absorbent material in mere proximity to thecomposite's fibrous component.

Referring to FIG. 11A, fluted absorbent composite 22 includesdistribution zones 26 that serve to rapidly acquire and distributeliquid to storage zones 24 and storage core 28. As noted above,distribution zones 26 are composed primarily of fibrous materials, andstorage zones 24 and core 28 are generally fibrous layers that includeabsorbent material. As described above, composite 22 can be formed byattaching bands of fibrous materials and absorbent materials to astorage core to form distribution zones 26 and storage zones 24,respectively. Alternatively, storage zones 24 can be formed integrallywith storage core 28 and, similarly, distribution zones 26 can also beintegrally formed with storage zones 24 and core 28. Although thedistributions zones are generally prepared from wet-laid composites, theabsorbent material containing storage zones can be made from air-laidcomposites. In one preferred embodiment, the distribution zones areformed from wet-laid fibrous composite that include fibrous materialssuitable for liquid acquisition and distribution, and the storage zonesand core are formed from air-laid fibrous composites that includeabsorbent material suitable for liquid storage. In another preferredembodiment, the storage zones and core are formed from a wet-laidcomposite. Generally, an absorbent composite having such a structure hasenhanced liquid acquisition compared to conventional storage cores andthose having relatively poor fluid communication between compositecomponents.

Multilayered absorbent constructs can also include the fluted absorbentcomposite of the present invention. One such construct is illustrated inFIG. 11B. Referring to FIG. 11B, absorbent construct 23 includes fibrouscomposite 22 and an acquisition layer 32 (e.g., formed primarily fromfibrous materials). As noted above composite 22 includes distributionzones 26, storage zones 24, and storage core 28.

Fluted composites having a unitary structure are generally preferredbecause of the intimate fluid communication between components (i.e.,regions of the composite) and for reasons relating to manufacturability.Accordingly, in a preferred embodiment, the fluted absorbent compositeis an integrally formed unitary structure.

The fluted absorbent composite of the present invention can be formedwet-laid and foam-forming processes. These general methodologies areknown to those of skill in the pulp processing art.

Preferably, the fluted absorbent composite is formed by a wet-laid or afoam-forming process. A representative example of a wet-laid process isdescribed in U.S. Pat. No. 5,300,192, issued Apr. 5, 1994, entitled“Wet-Laid Fiber Sheet Manufacturing with Reactivatable Binders forBinding Particles to Fibers”, expressly incorporated herein byreference. Wet-laid processes are also described in standard texts, suchas Casey, Pulp and Paper, 2edition, 1960, volume II, Chapter VIII-SheetFormation. Representative foam processes useful in forming the compositeof the present invention are known in the art and include thosedescribed in U.S. Pat. Nos. 3,716,449; 3,839,142; 3,871,952; 3,937,273;3,938,782; 3,947,315; 4,166,090; 4,257,754; and 5,215,627, assigned toWiggins Teape and related to the formation of fibrous materials fromfoamed aqueous fiber suspensions, and “The Use of an Aqueous Foam as aFiber-Suspending Medium in Quality Papermaking,” Foams, Proceedings of aSymposium organized by the Society of Chemical Industry, Colloid andSurface Chemistry Group, R. J. Akers, Ed., Academic Press, 1976, whichdescribes the Radfoam process, all expressly incorporated herein byreference.

Absorbent material is incorporated into the composite during theformation of the composite. Generally, the method for forming the flutedabsorbent composite includes depositing absorbent material into afibrous web, and then drying the web, as necessary, to provide thecomposite of the invention.

In a wet-laid method, absorbent material is preferably applied into afibrous slurry that has been deposited onto a foraminous support (i.e.,a forming wire). In the method, absorbent material is injected into anat least partially dewatered fibrous web formed by depositing a fibrousslurry onto a forming wire. The fibrous slurry preferably includesfibers and wet strength agent in a dispersion medium (e.g., a primarilyaqueous medium such as water). The absorbent material can be introducedinto the fibrous web as a dry particle or, preferably, as a liquidsuspension in an aqueous medium, preferably chilled (e.g., 34-40° F.)water. The absorbent material is generally injected into the partiallydewatered fibrous web immediately after the slurry's deposition onto theforming wire. The absorbent material is preferably deposited into thepartially dewatered fibrous web (i.e., before dewatering of the web iscompleted and during the formation of the wet composite where theconsistency of the web is increased relative to the slurry and, in anyevent, prior to the drying stage). After depositing the absorbentmaterial into the partially dewatered fibrous web, the web containingfibers and absorbent material is subjected to further removal of atleast a portion of the dispersion medium and water, preferably byvacuum, to provide a wet composite. The wet composite is then dried toprovide the absorbent composite.

It is desirable to inhibit liquid absorption by the absorbent materialduring the web formation process. To inhibit liquid absorption,absorbent material can be added to the at least partially dewatered webas an aqueous suspension in chilled water having a temperature in therange from about 0-5° C., preferably from about 0-3° C., and morepreferably about 1° C. Alternatively, the absorbent material can becooled to below 0° C., by placement or storage in a conventionalfreezer, and then forming a suspension in water, preferably chilledwater, immediately prior to web formation. Limiting the period of timethat the absorbent material is in contact with liquid during the formingprocess also has a positive effect on limiting absorbent material liquidabsorption. Preferably, the absorbent material suspension is added tothe at least partially dewatered fibrous web within about 10 seconds,and more preferably within about 5 seconds after preparing thesuspension.

By limiting the liquid absorption by the absorbent material during theformation process, web drying energy and/or time, and the consequentassociated expense can be greatly reduced. This advantage can result inweb formation processes that are more cost effective and can representsignificant savings for consumer absorbent products such as diapers,feminine care products, and adult incontinence products.

As described above, the absorbent composite of the present inventionincludes bands of absorbent material that are spaced laterally acrossthe composite's width and that extend longitudinally along thecomposite's length in the machine direction of the composite. Such aconfiguration of bands can be achieved by various methods includinginjecting absorbent material into the fibrous web, which has been atleast partially dewatered, through openings or nozzles spaced laterallyacross the width of the web. The nozzles are connected to an absorbentmaterial supply. The nozzles can be positioned in various configurationsand have orifices of varying size to provide bands having variousconfigurations including, for example, various widths. The absorbentmaterial is preferably deposited as a suspension in chilled water. Foraqueous suspensions, the absorbent material is injected as a stream orjet into the partially dewatered fibrous web. Injection of the streamcan result in significant mixing of the absorbent material and thefibers of the web. The degree of mixing can be controlled by severalfactors including stream velocity, web velocity, angle of injection, andposition of injection relative to the deposition of fibrous slurry onthe support, among others. Generally, the closer the absorbent materialinjection to the point at which dewatering of the fibrous web commences,the greater the mixing of absorbent material and fibers. Also, thegreater the mixing of absorbent material and fibers, the lesser theresulting concentration gradient of absorbent material in the composite.

Because the bands of absorbent material can be formed in the compositeby deposition or injection through individual nozzles, the nature andcharacteristics of the flutes that are ultimately formed in thecomposite can be controlled. For example, referring to the compositeillustrated in FIG. 3, the outermost flutes contain absorbent materialin relatively greater amounts compared to the inner flutes. Such acomposite can be formed by depositing greater concentrations ofabsorbent material, depositing absorbent material at a greater rate, orutilizing nozzles having larger diameter orifices for the outermostpositions. As noted above, absorbent materials having differentabsorptive and retentive capacities can be selectively deposited in thebands.

The deposition of individual bands also allows for the formation ofbands that can include materials in addition to absorbent material. Forexample, additional fibers can also be introduced into the depositedslurry through the use of these nozzles. Consequently, flutes havingadditional fibers, including fibers different from the deposited fibrousslurry, can be incorporated into the composite. In one preferredembodiment, the absorbent composite includes bands of absorbent materialthat further include additional fibers such as, for example, hardwoodfibers and/or synthetic fibers. The use of different fibers can be usedto form flutes having, for example, higher relative basis weights;greater bulk and softness; increased wicking; and increased rewetperformance. Thus, the composite's flutes can be formed from completelydifferent components compared to the base composite (i.e., the initiallydeposited fibrous slurry).

The composite's absorbent material enriched regions can be stabilized toenhance the structural integrity of the band or flute. Flute integritycan be enhanced by depositing, in addition to absorbent material, a wetstrength agent (e.g., Kymene®) and/or fibrous materials including, forexample, microfibrillated cellulose and fibrous superabsorbentmaterials. Fibrous superabsorbent materials are described in U.S. Pat.No. 5,607,550, expressly incorporated herein by reference.

The advantage of versatility allows for the design and formation ofvarious fluted absorbent composites. For example, the base composite canbe designed for strength and wicking, while the deposited bands can bedesigned to maximize swelling and absorbent capacity and to minimizerewet. More specifically, for an absorbent composite that maximizesabsorbent capacity, strength, and total material utilization, the basecomposite can include a mixture of southern pine fibers, eucalyptusfibers, crosslinked fibers and wet strength agent, and the bands caninclude a mixture of absorbent material and crosslinked cellulosicfibers or the fibers. For a composite having increased capacity andenhanced wicking to the absorbent material, the base composite caninclude a mixture of southern pine fibers, eucalyptus. fibers, and wetstrength agent, and the bands can include a mixture of absorbentmaterial, crosslinked cellulosic fibers, and microfibrillated cellulose.Another preferred absorbent composite includes a base composite composedof a refined mixture of crosslinked cellulosic fibers and eucalyptusfibers, and includes bands composed of a mixture of absorbent materialand unrefined crosslinked fibers. To reduce rewet, synthetic fibers(e.g., PET fibers) can be introduced into the composite by depositingthese fibers into the bands with absorbent material or including someabsorbent material in the composite's distribution zones. Theversatility of the method of the present invention enables the creationof fluted absorbent composites having a variety of compositions andabsorbent properties.

The method of the present invention also allows for the deposition offoam dispersions as bands of materials into a fibrous slurry. In oneembodiment, the composite has a wet-laid fibrous base and foam-formedbands. In another embodiment, the composite includes a foam-formedfibrous base and wet-laid bands and, in still another embodiment, thecomposite includes a foam-formed fibrous base and bands. The ability todeposit a foam dispersion enables the use of a wide range of fibertypes, lengths, and deniers in the composite's absorbent bands. Byselection of fibers, the bands (and ultimately the composite's flutes)can be, for example, soft and have a degree of stretch. By forming acomposite having stretch capabilities, a shaped core can be formed froma rectangular composite, thus eliminating the need to shape the core bycutting, which results in material waste. Such a core also has thegreatest density of absorbent material in the crotch area, the site ofliquid insult.

As noted above, the absorbent composite of the present invention can beformed from a combination of fibers, and optionally wet strength agent,in a dispersion medium, and absorbent material. In one embodiment, afibrous slurry is formed by directly combining fibers, and optionallywet strength agent, in a dispersion medium followed by the addition ofabsorbent material, preferably as a liquid suspension of chilled water,to an at least partially dewatered fibrous web on a foraminous support.In another embodiment, absorbent material is added to the partiallydewatered fibrous web on a foraminous support in combination with fibersas a slurry containing fibers and absorbent material. Such a slurry canbe prepared by first combining fibers with a dispersion medium to whichis then added absorbent material in a second step.

Once the fibrous slurry is deposited onto the foraminous support, thedispersion medium begins to drain from the deposited slurry to providean at least partially dewatered fibrous web. Removal of the dispersionmedium (e.g., water) from the deposited fibrous slurry (i.e., thepartially dewatered web) continues through, for example, the applicationof pressure, vacuum, and combinations thereof, and results in theformation of a wet composite.

The absorbent composite of the present invention is ultimately producedby drying the wet composite. Drying removes at least a portion of theremaining dispersion medium and water and provides an absorbentcomposite having the desired moisture content. Suitable composite dryingmethods include, for example, the use of drying cans, air floats andthrough air dryers. Other drying methods and apparatus known in the pulpand paper industry may also be used. Drying temperatures, pressures andtimes are typical for the equipment and methods used, and are known tothose of ordinary skill in the art in the pulp and paper industry.

For foam methods, the fibrous slurry is an aqueous or foam slurry thatfurther includes a surfactant. Suitable surfactants include ionic,nonionic, and amphoteric, surfactants known in the art.

The deposition of the components of the absorbent composite onto theforaminous support ultimately results in the formation of a wetcomposite that includes absorbent material that may have absorbed waterand, as a result, swollen in size. Water is withdrawn from the wetcomposite containing the water-swollen absorbent material distributed onthe support and the-wet composite dried.

In the methods of the present invention, the absorbent materialpreferably absorbs less than about 20 times its weight in the dispersionmedium, more preferably less than about 10 times, and even morepreferably less than about 5 times its weight in the dispersion medium.Other preferable absorbent materials include materials that absorbliquid only after prolonged contact with liquid, or that absorb liquidonly under certain conditions, and do not absorb any significant amountof liquid during the forming process.

Foam methods are advantageous for forming the absorbent composite of thepresent invention for several reasons. Generally, foam methods providefibrous webs that possess both relatively low density and relativelyhigh tensile strength. For webs composed of substantially the samecomponents, foam-formed webs generally have densities greater thanair-laid webs and lower than wet-laid webs. Similarly, the tensilestrength of foam-formed webs is substantially greater than for air-laidwebs and approach the strength of wet-laid webs. Also, the use offoam-forming technology allows better control of the orientation anduniform distribution of fibers and the incorporation of a wide range ofmaterials (e.g., long and synthetic fibers that cannot be readilyincorporated into wet-laid processes) into the composite.

One machine for implementing the method of the present invention is aconventional papermaking machine (wet-laid pulp machine) that has beenmodified to include a plurality of nozzles positioned downstream fromthe headbox outlet. Generally, the nozzles are spaced laterally atintervals, for example, regular intervals, across the width of the web.As described above, the nozzles are connected to an absorbent materialsupply and, in a preferred embodiment, a chilled aqueous suspension ofabsorbent material is pumped to the nozzles to form an aqueous stream orjet that impinges on and penetrates the surface of the deposited fibrousslurry (i.e., partially dewatered web) as the wet composite is formed.Because the wet composite is moving away from the headbox as it isformed, bands of absorbent material are created in the composite alongthe machine direction. Through the use of vacuum, the machine drainswater from the composite. The wet composite is then dried to provide thefinal product. A diagrammatic view of a representative machine andmethod for forming the fluted absorbent composite of the presentinvention is illustrated in FIG. 12A.

Referring to FIG. 12A, machine 100 includes foraminous support 102(i.e., a forming wire); vacuum heads 104 for dewatering fibrous slurry124 to provide wet composite 120; headbox 106 for depositing the fibrousslurry onto support 102; nozzle manifold 108 for injecting absorbentmaterial 122, preferably as an aqueous suspension, into partiallydewatered web 126; fibrous slurry supply 112; absorbent material supply114; pumps 110 for delivering the fibrous slurry and absorbent materialfrom their respective supplies to headbox 106 and manifold 108,respectively; and drying means 116. Briefly, fibrous slurry 124 isdeposited from headbox 106 onto support 102 and dewatered to providepartially dewatered web 126. Absorbent material 122, preferably as anaqueous suspension, is injected through nozzle manifold 108 intopartially dewatered web 126, preferably prior to extensive dewatering atvacuum heads 104. As described above, manifold 108 includes a pluralityof nozzles positioned across the width of support 102 (i.e., thecross-machine direction) to deliver and inject absorbent material inbands across the composite's width. Wet composite 120 is furtherdewatered along support 102 and then dried by drying means 116 (e.g.,heated cans, drying oven, through-air dryer). A top plan view of theinjection of absorbent material into the fibrous slurry is illustratedin FIG. 12B.

The absorbent composite of the invention can be formed by devices andprocesses that include a twin-wire configuration (i.e., twin-formingwires). A representative twin-wire machine for forming composites of theinvention is shown in FIG. 13. Referring to FIG. 13, machine 200includes twin-forming wires 202 and 204 into which the composite'scomponents are deposited. Basically, fibrous slurry 124 is introducedinto headbox 212 and deposited onto forming wires 202 and 204 at theheadbox exit. Vacuum elements 206 and 208 dewater the fibrous slurriesdeposited on wires 202 and 204, respectively, to provide partiallydewatered webs that exit the twin-wire portion of the machine aspartially dewatered web 126. Web 126 continues to travel along wire 202and continues to be dewatered by additional vacuum elements 210 toprovide wet composite 120 which is then dried by drying means 216 toprovide composite 10.

Absorbent material can be introduced into the fibrous web at any one ofseveral positions in the twin-wire process depending on the desiredproduct configuration. For example, absorbent material can be introducedafter the partially dewatered fibrous web has exited the twin-wireportion of the machine and has traveled along wire 202. Referring toFIG. 13, absorbent material 122 can be injected onto partially dewateredfibrous web 126 at position 1. Alternatively, absorbent material can beintroduced into the partially dewatered fibrous web prior to the webexiting the twin-wire portion of the machine (i.e., in the headbox).Referring to FIG. 13, absorbent material 122 can be injected into thepartially dewatered web at positions 2, 3, or 4, or other positionsalong wires 202 and 204 where the web has been at least partiallydewatered. Absorbent material can be introduced into the partiallydewatered web formed and traveling along wire 202 and/or 204. As notedabove, to form the composite of the invention having bands of absorbentmaterial extending in the composite's machine direction, absorbentmaterial is injected into the partially dewatered fibrous webs bynozzles spaced laterally across the width of the web. The nozzles areconnected to an absorbent material supply. The nozzles can be positionedin various positions (e.g., positions 1, 2, or 3 in FIG. 13) asdescribed above. For example, referring to FIG. 13, nozzles can belocated at positions 2 to inject absorbent material into partiallydewatered webs on wires 202 and 204. Generally, the extent of mixing offibers with absorbent material decreases as the fibrous web is dewatered(e.g., less mixing at position 1 than at position 2, and less mixing atposition 2 than at position 3).

Depending on the position of absorbent material introduction, thetwin-wire method for forming the composite of the present invention canprovide a composite having a fibrous stratum. Representative compositesof the invention having fibrous strata formed by the twin-wire method ofthe present invention are shown in FIGS. 14A-H. Referring to FIG. 14A,representative composites 10 include regions 12 enriched with absorbentmaterial, distribution zones 14 substantially free of absorbentmaterial, and fibrous strata 11 coextensive with the outward surfaces ofcomposite 10.

Referring to FIG. 14A, composite 10 can be formed by a method thatintroduces absorbent material into a single partially dewatered web(i.e., a web traveling on wire 202 or 204). FIGS. 14B and 14C depictsimilarly formed composites having absorbent material extending into thecomposite to relatively greater depths (i.e., z-direction penetration).Referring to FIG. 14D, composite 10 includes absorbent materialintroduced into the center fibrous. Such a composite can be formed byadjusting the depth of absorbent material penetration by, for example,nozzle distance from the forming wire or absorbent material injectionangle.

Alternatively, the composite of the invention can be formed by atwin-wire method that introduces absorbent material into both partiallydewatered webs (i.e., webs traveling on wires 202 and 204). Such amethod includes a two sets of nozzles, a first nozzle set for injectioninto one partially dewatered web, and a second nozzle set for injectioninto the other partially dewatered web. Referring to FIG. 14E, composite10 includes regions enriched with absorbent material that extendsubstantially throughout the composite's depth (i.e., z-direction). Sucha composite configuration can be formed from a pair of nozzle sets thatare either positioned or timed to provide absorbent material bands thatalign in the z-direction. Offsetting one set of nozzles from the other,or providing nonsynchronous absorbent material pulses from a pair ofaligned nozzle sets, provides composites having offset bands ofabsorbent material. Such a composite configuration is illustrated inFIG. 14F. FIGS. 14G and 14H illustrate composites formed by methodssimilar to those which provide the composites shown in FIGS. 14E and14F, respectively, but in contrast to those composites, the compositesof FIGS. 14G and 14H are formed by the introduction of absorbentmaterial to a penetration depth less than that of the composites inFIGS. 14E and 14F.

As shown in FIG. 14, the composite of the present invention can includeintegrated phases having fibrous strata coextensive with the outwardsurfaces of the composite. These fibrous composites can be formed frommultilayered inclined formers or twin-wire formers with sectionedheadboxes. These methods can provide stratified or phased compositeshaving strata or phases having specifically designed properties andcontaining components to attain composites having desired properties.The composite's regions of enriched absorbent material (i.e., thecomposite's absorbent bands) can be located throughout the z-directionby adjusting the basis weights of the upper and lower strata.

Basically, the position of the absorbent material band in thecomposite's z-direction effectively defines the fibrous stratum coveringthe band. For a formation method that includes a single fiber furnish,the band position can be adjusted by positioning the absorbent materialinjection system (e.g., nozzle set) in relation to the forming wire. Formethods that include multiple furnishes, the upper and lower strata canbe composed of the same or different components and introduced into asectioned headbox.

Referring to FIGS. 13 and 14A, composite 10 having strata 11 can beformed by machine 200. For composites in which strata 11 comprise thesame components, a single fiber furnish 124 is introduced into headbox212. For forming composites having strata 11 comprising differentcomponents, headbox 212 includes one or more baffles 214 for theintroduction of fiber furnishes (e.g., 124 a, 124 b, and 124 c) havingdifferent compositions. In such a method, the upper and lower strata canbe formed to include different components and have different basisweights and properties.

Preferably, the fluted composite is formed by a foam-forming methodusing the components described above. In the foam-forming method,fibrous webs having multiple strata and including bands of absorbentmaterial can be formed from multiple fibrous slurries. In a preferredembodiment, the foam-forming method is practiced on a twin-wire former.

The method can provide a variety of multiple strata compositesincluding, for example, composites having three strata. A representativecomposite having three strata includes a first stratum formed fromfibers (e.g., synthetic fibers, cellulosic, and/or binder fibers); anintermediate stratum formed from fibers and/or other absorbent materialsuch as superabsorbent material; and a third stratum formed from fibers.The method of the invention is versatile in that such a composite canhave relatively distinct and discrete strata or, alternatively, havegradual transition zones from stratum-to-stratum.

A representative method for forming a fibrous web having an intermediatestratum generally includes the following steps:

-   -   (a) forming a first foam fibrous slurry comprising fibers and a        surfactant in an aqueous dispersion medium;    -   (b) forming a second foam fibrous slurry comprising fibers and a        surfactant in an aqueous dispersion medium;    -   (c) moving a first foraminous element (e.g., a forming wire) in        a first path;    -   (d) moving a second foraminous element in a second path;    -   (e) passing the first foam slurry into contact with the first        foraminous element moving in a first path;    -   (f) passing the second foam slurry into contact with the second        foraminous element moving in the second path;    -   (g) passing a third material between the first and second foam        slurries such that the third material does not contact either of        the first or second foraminous elements; and    -   (h) forming a fibrous web from the first and second foam        slurries and third material by withdrawing foam and liquid from        the slurries through the first and second foraminous elements.

As noted above, the method is suitably carried out on a twin-wireformer, preferably a vertical former, and more preferably, a verticaldownflow twin-wire former. In the vertical former, the paths for theforaminous elements are substantially vertical.

A representative vertical downflow twin-wire former useful in practicingthe method of the invention is illustrated in FIG. 15. Referring to FIG.15, the former includes a vertical headbox assembly having a former witha closed first end (top), closed first and second sides and an interiorvolume. A second end (bottom) of the former is defined by moving firstand second foraminous elements, 202 and 204, and forming nip 213. Theinterior volume defined by the former's closed first end, closed firstand second sides, and first and second foraminous elements includes aninterior structure 230 extending from the former first end and towardthe second end. The interior structure defines a first volume 232 on oneside thereof and a second volume 234 on the other side thereof. Theformer further includes supply 242 and means 243 for introducing a firstfiber/foam slurry into the first volume, supply 244 and means 245 forintroducing a second fiber/foam slurry into the second volume, andsupply 246 and means 247 for introducing a third material into theinterior structure. Means for withdrawing foam (e.g., suction boxes 206and 208) from the first and second slurries through the foraminouselements to form a web are also included in the headbox assembly.

In the method, the twin-wire former includes a means for introducing atleast a third material through the interior structure in such a way thatthe third material forms bands or stripes in the resulting web.Preferably, the introducing means include at least a first plurality ofconduits having a first effective length. A second plurality of conduitshaving a second effective length different from the first length mayalso be used. More than two sets of conduits can also be used.

Another representative vertical downflow twin-wire former useful inpracticing the method of the invention is illustrated in FIG. 16.Referring to FIG. 16, the former includes a vertical headbox assemblyhaving an interior volume defined by the former's closed first end,closed first and second sides, and first and second foraminous elements,202 and 204, and includes an interior structure 230 extending from theformer first end and toward the second end. In this embodiment, interiorstructure 230 includes plurality of conduits 235 and 236, and optionaldivider walls 214.

The interior structure defines a first volume 232 on one side thereofand a second volume 234 on the other side thereof. The former furtherincludes supply 242 and means 243 for introducing a first fiber/foamslurry into the first volume, supply 244 and means 245 for introducing asecond fiber/foam slurry into the second volume, supply 246 and means247 for introducing a third material into plurality of conduits 236,supply 248 and means 249 for introducing a third material into pluralityof conduits 235, and supply 250 and means 251 for introducing anothermaterial, such as a foam slurry, within the volume defined by walls 214.

Plurality of conduits 235 can have an effective length different fromplurality of conduits 236. The third material can be introduced throughconduits 235 and 236, or, alternatively, a third material can beintroduced through conduits 235 and a fourth material can be introducedthrough conduits 236. Preferably, the ends of conduits 235 and 236terminate at a position beyond where the suction boxes begin withdrawingfoam from the slurries in contact with the foraminous elements (i.e.,beyond the point where web formation begins). Plurality of conduits 235and/or 236 are suitable for introducing stripes or bands of thirdmaterial in fibrous webs formed in accordance with the presentinvention. Plurality of conduits 235 and 236 can be moved in a firstdimension toward and away from nip 213, and also in a second dimensionsubstantially perpendicular to the first, closer to one forming wire orthe other. Representative plurality of conduits 235 and 236 areillustrated in FIG. 17.

Generally, the former's interior structure (i.e., structure 230 in FIGS.15 and 16) is positioned with respect to the foraminous elements suchthat material introduced through the interior structure will notdirectly contact the first and second foraminous elements. Accordingly,material is introduced through the interior structure between the firstand second slurries after the slurries have contacted the foraminouselements and withdrawal of foam and liquid from those slurries hascommenced. Such a configuration is particularly advantageous forintroducing superabsorbent materials and for forming stratifiedstructures in which the third material is a foam/fiber slurry. Dependingupon the nature of the composite to be formed, the first and secondfiber/foam slurries may be the same, or different, from each other andfrom the third material.

In a preferred embodiment, the method includes introducing the thirdmaterial at a plurality of different points to provide a compositehaving bands or stripes of third material within the product. Thepositions of at least some of the plurality of different points forintroducing the third material into the headbox can be adjusted when itis desired to adjust the introduction point in a first dimension towardand away from the headbox exit (i.e., nip 213 in FIGS. 15 and 16); andto adjust at least some of the plurality of points in a second dimensionsubstantially perpendicular to the first dimension, closer to oneforming wire or the other.

The method can also include utilizing a plurality of distinct conduits,the conduits being of at least two different lengths, for introducingthe third material into the headbox. The method can also be utilized inheadboxes having dividing walls that extend part of the length of theconduits toward the headbox exit. Such headboxes are illustrated inFIGS. 13 and 16.

The means for introducing first and second foam slurries into the firstand second volumes can include any conventional type of conduit, nozzle,orifice, header, or the like. Typically, these means include a pluralityof conduits are provided disposed on the first end of the former andfacing the second end.

The means for withdrawing foam from the first and second slurriesthrough the foraminous elements to form a web on the foraminous elementsare also included in the headbox assembly. The means for withdrawingfoam can include any conventional means for that purpose, such assuction rollers, pressing rollers, or other conventional structures. Ina preferred embodiment, first and second suction box assemblies areprovided and mounted on the opposite sides of the interior structurefrom the foraminous elements (see boxes 206 and 208 in FIGS. 13, 15, and16).

The fluted absorbent composite can be incorporated as an absorbent coreor storage layer in an absorbent article including, for example, adiaper or feminine care product. The absorbent composite can be usedalone, or as illustrated in FIGS. 18 and 19, can be used in combinationwith one or more other layers. FIG. 18 illustrates absorbent construct30 where composite 10 is employed as a storage layer in combination withan upper acquisition layer 32. As illustrated in FIG. 19 illustratingconstruct 40, a third layer 42 (e.g., distribution layer) can also beemployed, if desired, with composite 10 and acquisition layer 32.

The fluted absorbent composite can also be incorporated as a liquidmanagement layer in an absorbent article such as a diaper. In such anarticle, the composite can be used in combination with a storage core orlayer. In the combination, the liquid management layer can have asurface area that is smaller than, the same size as, or slightly greaterthan the surface area of the storage layer's surface facing the flutedcomposite. Representative absorbent constructs that incorporate thefluted composite in combination with a storage layer are shown in FIGS.20 and 21. Referring to FIG. 20, absorbent construct 90 includes flutedcomposite 10 and storage layer 60. Storage layer 60 is preferably afibrous layer that includes absorbent material. The storage layer can beformed by any method including air-laid, wet-laid, and foam-formingmethods.

For constructs that include a storage layer and the fluted composite asan liquid management layer, the absorbent material in the flutedcomposite can be the same, similar, or different from the absorbentmaterial in the storage layer.

In certain embodiments, the fluted absorbent composite is asymmetric inthat the composite's facing and backing surfaces are not identical. Inthese embodiments, the composite has a first surface into whichabsorbent material has been injected and an opposing surface (i.e.,machine side) composed substantially of fibers and which constitutes asurface of the composite's fibrous base. For absorbent constructs thatcontain, in addition to the fluted composite, a storage layer, thecomposite can be oriented in two ways. In one embodiment, the flutedcomposite is oriented with its fluted surface directed toward thewearer. A representative construct 90 having a storage layer and flutedcomposite having its fluted surface directed toward the wearer is shownin FIG. 20. Alternatively, as shown in FIG. 21, representative construct92 includes composite 10 having the composite's flutes directed towardstorage layer 60. The surface of the storage layer may or may notconform to the surface of the fluted composite.

It is anticipated that the rewet of constructs that include the flutedcomposite can also be reduced by incorporating synthetic fibers (e.g.,hydrophobic fibers such as polyester fibers) into the composite'sfibrous base. When used in combination with a storage layer, the flutedcomposite having a fibrous base that includes synthetic (hydrophobic)fibers is preferably incorporated into the construct in the invertedconfiguration.

To further enhance rewet performance, an acquisition layer can becombined with the fluted composite and storage layer. FIGS. 22 and 23illustrate absorbent constructs 94 and 96, respectively, each havingacquisition layer 32 overlaying composite 10 and storage layer 60.

Constructs 90, 92, 94, and 96 can further include intermediate layer 70to provide constructs 100, 102, 104, and 106, shown in FIGS. 24A through24D, respectively. Intermediate layer 70 can be, for example, a tissuelayer, a nonwoven layer, an air-laid or wet-laid pad, or a flutedcomposite.

Constructs 90, 92, 94, 96, 100, 102, 104, and 106 can be incorporatedinto absorbent articles. Generally, absorbent articles 110, 112, 114,116, 120, 122, 124, and 126, shown in FIGS. 25A through 25H,respectively, include a liquid pervious facing sheet 52 and a liquidimpervious backing sheet 54 and constructs 90, 92, 94, 96, 100, 102,104, and 106, respectively. In such absorbent articles, the facing sheetis joined to the backing sheet.

A variety of suitable constructs can be produced from the absorbentcomposite. The most common include absorptive consumer products, such asdiapers, feminine hygiene products such as feminine napkins, and adultincontinence products. For example, referring to FIGS. 26A and 26B,absorbent article 50 includes absorbent composite 10 and has a liquidpervious facing sheet 52 and a liquid impervious backing sheet 54. Asshown in FIG. 26B, facing sheet 52 is joined to backing sheet 54.Referring to FIG. 27, absorbent article 60 includes absorbent composite10 and an overlying acquisition layer 32. A liquid pervious facing sheet52 overlies acquisition layer 32, and a liquid impervious backing sheet54 underlies absorbent composite 10. These absorbent composites willprovide advantageous liquid absorption performance for use in, forexample, diapers. FIG. 28 illustrates absorbent construct 70, whichfurther includes distribution layer 42 interposed between acquisitionlayer 32 and composite 10. As described above, the fluted structure ofthe absorbent composite aids in fluid transport and absorption inmultiple wettings.

One of ordinary skill will be able to make a variety of differentconstructs using the concepts taught herein. For example, a typicalconstruction of an adult incontinence absorbent structure is shown inFIG. 29. The article 80 includes facing sheet 52, acquisition layer 32,absorbent composite 10, and backing sheet 54. Facing sheet 22 ispervious to liquid while backing sheet 24 is impervious to liquid. Inthis construct, a liquid pervious tissue 44 composed of a polar, fibrousmaterial is positioned between absorbent composite 10 and acquisitionlayer 32.

The present invention provides a fibrous absorbent composite containingabsorbent material and methods for its formation. The absorbentcomposite is a fibrous structure that includes absorbent materialdispersed in bands along the composite's length. Between the bands ofabsorbent material, the absorbent composite has continuously opendistribution zones that preclude gel blocking in the composite. Afterinitial liquid insult, the composite develops flutes that open thefibrous structure and increase the liquid acquisition rate forsubsequent liquid insults. The combination of flutes and distributionzones allows for total utilization of the absorbent composite as astorage core when incorporated into an absorbent article such as adiaper. The fluted absorbent composite can be advantageously used as aliquid management layer or a storage core in absorbent articles such asdiapers.

The following examples are provided for the purpose of illustrating, andnot limiting, the invention.

EXAMPLES Example 1 Acquisition Times for a Representative FlutedAbsorbent Composite

In this example, the acquisition time for a representative flutedabsorbent composite of the present invention (Composite A) is comparedto a commercially available diaper (Diaper A, Kimberly-Clark). Alsoincluded in the comparison is an absorbent composite (Composite B)having a composition similar to the composite of the invention andcomposed of fibers (50:50 crosslinked fibers and southern pine pulpfibers), wet strength agent, and absorbent material distributedrelatively uniformly throughout the composite. The formation ofComposite B is described in provisional U.S. patent application Ser. No.60/046,395, filed May 13, 1997, and international application Serial No.PCT/US98/09682, filed May 12, 1998, assigned to Weyerhaeuser Company,each expressly incorporated herein by reference.

The tests were conducted on commercially available diapers(Kimberly-Clark) from which the core and surge management layer wereremoved and used as surrounds for the fluted absorbent composite and forComposite B. The test diapers were prepared by inserting the flutedabsorbent composite or Composite B into the diapers.

The aqueous solution used in the tests is a synthetic urine availablefrom National Scientific under the trade name RICCA. The synthetic urineis a saline solution containing 135 meq./L sodium, 8.6 meq./L calcium,7.7 meq./L magnesium, 1.94% urea by weight (based on total weight), plusother ingredients.

A sample of the absorbent structure is prepared for the test bydetermining the center of the structure's core, measuring 1 inch to thefront for liquid application location, and marking the location with an“X.” Once the sample is prepared, the test is conducted by first placingthe sample on a plastic base (4¾ inch×19¼ inch) and then placing afunnel acquisition plate (4 inch×4 inch plastic plate) on top of thesample with the plate's hole positioned over the “X”. A donut weight(1400 g) is then placed on top of the funnel acquisition plate, to whichis then attached a funnel (4 inch diameter). Liquid acquisition is thendetermined by pouring 100 mL synthetic urine into the funnel andmeasuring the time from when liquid is first introduced into the funnelto the time that liquid disappears from the bottom of the funnel intothe sample. The measured time is the acquisition time for the firstliquid insult. After waiting 1 minute, a second 100 mL portion is addedto the funnel and the acquisition time for the second insult ismeasured. After waiting an additional 1 minute, the acquisition isrepeated for a third time to provide an acquisition time for the thirdinsult. The acquisition times reported in seconds for each of the threesuccessive 100 mL liquid insults for Diaper A, Composite B, andComposite A are summarized in Table 1. TABLE 1 Acquisition TimeComparison Acquisition Time (sec) Insult Diaper A Composite B CompositeA 1 45 10 10 2 60 11 6 3 75 10 4

As shown in Table 1, liquid is more rapidly acquired by the absorbentcomposite of the invention than for the commercially available diapercontaining an air-laid storage core. The results show that the air-laidcore does not acquire liquid nearly as rapidly as the wet-laid compositeof the invention. The commercial diaper also exhibited characteristicdiminution of acquisition rate on successive liquid insults. Incontrast, the composite of the invention shows a decrease in acquisitiontime as the composite continued to absorb liquid on successive insult.Significantly, the absorbent composite of the invention exhibits anacquisition time for the third insult that is substantially less (about10-fold) than that of the commercially available diaper for initialinsult. The results reflect the greater wicking ability and capillarynetwork for the wet-laid composites compared to conventional air-laidstorage cores in general, and the enhanced performance of the flutedabsorbent composite in particular.

For the reasons noted above, the observed acquisition time for wet-laidComposite B is also less than for the air-laid core. The acquisitiontimes for Composite B on successive insults remain substantiallyconstant. In contrast, Composite A exhibits a greatly reducedacquisition times on the second and third insults. The increased rate isattributable to the banded nature of the absorbent material in thecomposite. Thus, the results show that even among wet-laid compositescontaining absorbent material, the configuration of absorbent materialwithin the composite is a significant factor in liquid acquisition.Whereas homogeneously distributed absorbent material in a wet-laidcomposite provides advantages over similarly composed air-laidcomposites, wet-laid composites having bands of absorbent materialprovide further significant advantages including enhanced and persistentliquid acquisition.

Example 2 Acquisition Rate and Rewet for Representative Fluted AbsorbentComposites

In this example, the acquisition time and rewet of representative flutedabsorbent composites of the present invention (designated CompositesA1-A4) are compared to a commercially available diaper (Diaper A,Kimberly-Clark). Composites A1-A4 differ by the method by which thecomposites were dried. Also included in the comparison are a series ofabsorbent composites (Composites B1-B4) formed as described above forComposite B in Example 1 and differing by the method by which they weredried.

Certain properties of the tested composites including the amount ofsuperabsorbent polymeric material (weight percent SAP) in the compositeand basis weight for each of the composites are summarized in Table 2.

The tests were conducted on commercially available diapers(Kimberly-Clark) from which the cores were removed and used as surroundsfor the fluted absorbent composites and for Composites B1-B4. The testdiapers were prepared by inserting the tested composites into thediapers.

The acquisition time and rewet are determined in accordance with themultiple-dose rewet test described below.

Briefly, the multiple-dose rewet test measures the amount of syntheticurine released from an absorbent structure after each of three liquidapplications, and the time required for each of the three liquid dosesto wick into the product.

The aqueous solution used in the tests is a synthetic urine availablefrom National Scientific under the trade name RICCA, and as describedabove in Example 1.

A preweighed sample of the absorbent structure is prepared for the testby determining the center of the structure's core, measuring 1 inch tothe front for liquid application location, and marking the location withan “X.” A liquid application funnel (minimum 100 mL capacity, 5-7 mL/sflow rate) is placed 4 inches above surface of sample at the “X.” Oncethe sample is prepared, the test is conducted as follows. Flatten thesample, nonwoven side up, onto a table top under the liquid applicationfunnel. Fill the funnel with a dose (100 mL) of synthetic urine. Place adosing ring ( 5/32 inch stainless steel, 2 inch ID×3 inch height) ontothe “X” marked on the samples. Apply a first dose of synthetic urinewithin the dosing ring. Using a stopwatch, record the liquid acquisitiontime in seconds from the time the funnel valve is opened until theliquid wicks into the product from the bottom of the dosing ring. Waittwenty minutes. During the twenty minute wait period after the firstdose is applied, weigh a stack of filter papers (19-22 g, Whatman #3,11.0 cm or equivalent, that have been exposed to room humidity forminimum of 2 hours before testing). The stack of preweighed filterpapers are placed on the center of the wetted area. A cylindrical weight(8.9 cm diameter, 9.8 lb.) is placed on top of these filter papers.After two minutes the weight is removed, the filter papers are weighedand the weight change recorded. The procedure is repeated two moretimes. A second dose of synthetic urine is added to the diaper, and theacquisition time is determined, filter papers are placed on the samplefor two minutes, and the weight change determined. For the second dose,the weight of the dry filter papers is 29-32 g, and for the third dose,the weight of the filter papers is 39-42 g. The dry papers from theprior dosage are supplemented with additional dry filter papers.

Liquid acquisition time is reported as the length of time (seconds)necessary for the liquid to be absorbed into the product for each of thethree doses. The results are summarized in Table 2.

Rewet is reported as the amount of liquid (grams) absorbed back into thefilter papers after each liquid dose (i.e., difference between theweight of wet filter papers and the weight of dry filter papers). Theresults are also summarized in Table 2. TABLE 2 Acquisition Time andRewet Comparison Acquisition Time Rewet SAP % Basis Weight (Sec) (g)Composite (w/w) (gsm) Insult 1 Insult 2 Insult 3 Insult 1 Insult 2Insult 3 A1 45.0 668 20 16 18 0.1 0.2 0.5 A2 39.3 665 19 16 19 0.1 0.20.5 A3 37.0 715 26 16 17 0.1 0.2 0.5 A4 46.0 710 18 16 24 0.1 0.1 0.3 B149.4 568 16 19 26 0.1 0.4 2.4 B2 38.3 648 17 19 22 0.1 0.7 2.5 B3 35.9687 29 26 27 0.2 0.2 0.7 B4 38.8 672 17 18 21 0.1 0.3 0.9 Commercial40.0 625 34 35 39 0.1 4.0 12.6 air-laid core

As indicated in Table 2, the acquisition times for representativecomposites of the invention (Composites A1-A4) were significantly lessthan for the commercially available core.

The rewet of the representative composites of the invention (CompositesA1-A4) is significantly less than for the other cores. While most of thecomposites exhibited relatively low rewet initially, after the thirdinsult the commercially available core showed substantial rewet. Incontrast, Composites A continued to exhibit low rewet.

Example 3 Horizontal and Vertical Wicking for a Representative FlutedAbsorbent Composite

In this example, the wicking characteristics of a representative flutedabsorbent composite (Composite A) are compared to a commerciallyavailable diaper storage core (Diaper B, Procter & Gamble) and awet-laid storage core having absorbent material distributed uniformlythroughout the composite (Composite B).

The horizontal wicking test measures the time required for liquid tohorizontally wick preselected distances. The test is performed byplacing a sample composite on a horizontal surface with one end incontact with a liquid bath and measuring the time required for liquid towick preselected distances. Briefly, a sample composite strip (40 cm×10cm) is cut from a pulp sheet or other source. If the sheet has a machinedirection, the cut is made such that the 40 cm length of the strip isparallel to the machine direction. For absorbent composites of theinvention, the strip is centered such that four bands of absorbentmaterial are within the strip's width. Starting at one end of the 10 cmwidth of the strip mark a first line at 4.5 cm from the strip edge andthen mark consecutive lines at 5 cm intervals along the entire length ofthe strip (i.e., 0 cm, 5 cm, 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, and 35cm). Prepare a horizontal wicking apparatus having a center trough withlevel horizontal wings extending away from opposing sides of the trough.The nonsupported edge of each wing being flush with the inside edge ofthe trough. On each wings' end place a plastic extension to support eachwing in a level and horizontal position. The trough is then filled withsynthetic urine. The sample composite strip is then gently bent at the4.5 cm mark to form an approximately 45 angle in the strip. The strip isthen placed on the wing such that the strip lays horizontally and thebent end of the strip extend into and contacts the liquid in the trough.Begin timing liquid wicking when the liquid reaches the first linemarked on the composite 5 cm from the 4.5 cm bend. The wicking time isthen recorded at 5 cm intervals when 50 percent of the liquid frontreaches the marked interval (e.g., 5 cm, 10 cm). The liquid level in thetrough is maintain at a relatively constant level throughout the test byreplenishing with additional synthetic urine. The horizontal wickingresults are summarized in Table 3. TABLE 3 Horizontal Wicking ComparisonDistance Wicking Time (sec) (cm) Diaper B Composite B Composite A 5 4815 11 10 150 52 27 15 290 134 67 20 458 285 142 25 783 540 250 30 17031117 350 35 — 1425 480

The results tabulated above indicate that horizontal wicking is enhancedfor the wet-laid composites compared to a conventional air-laid core.While the wicking time for Composite B is about 50 percent of that forthe conventional diaper core, the wicking time for Composite A is about50 percent of that for Composite B. Thus, the horizontal wicking forComposite A is about four times that of a commercially available storagecore. Such a result indicates the effectiveness of the distributionzones of the composite of the present invention created by the bandednature of the absorbent material.

The vertical wicking test measures the time required for liquid tovertically wick preselected distances. The test is performed byvertically suspending a sample composite with one end of the compositein contact with a liquid bath and measuring the time required for liquidto wick preselected distances. Prior to the test, sample composites (10cm×22 cm) are cut and marked with consecutive lines 1 cm, 11 cm, 16 cm,and 21 cm from one of the strip's edges. Preferably, samples arepreconditioned for 12 hours at 50 percent relative humidity and 23° C.and then stored in sample bags until testing. The sample composite isoriented lengthwise vertically and clamped from its top edge at the 1 cmmark and allowing its bottom edge to contact bath containing syntheticurine. Timing commences once the strip is contacted with the liquid. Thetime required for 50 percent of the wicking front to reach 5 cm, 10 cm,15 cm, and 20 cm is then recorded. The vertical wicking results in Table4. TABLE 4 Vertical Wicking Comparison Distance Wicking Time (sec) (cm)Diaper B Composite B Composite A 5 20 6 11 10 Fell Apart 54 51 15 — 513257 20 — 3780 1110

As for the horizontal wicking results, wet-laid Composites A and B havesignificantly greater vertical wicking. Moreover, as between CompositesA and B, the composite of the present invention can distribute liquidremote from insult more rapidly than even for the wet-laid compositehaving absorbent material distributed. uniformly throughout thecomposite. The results also show that the wet-laid composites havesignificantly greater wet tensile strength compared to the conventionalair-laid composite.

Example 4 Liquid Distribution for a Representative Fluted AbsorbentComposite

In this example, the distribution of liquid in a fluted absorbentcomposite (Composite A) is compared to that of two commerciallyavailable diapers (Diapers A and B above). The test measures thecapacity of a diaper core to distribute acquired liquid. Perfectdistribution would have 0% deviation from average. Ideal liquiddistribution would result in equal distribution of the applied liquid ineach of the four distribution zones (i.e., about 25% liquid in eachzone).

Liquid distribution is determined by weighing different zones of asample that has been subjected to the multiple-dose rewet test describedabove in Example 2. Basically, after the last rewet, the wings of thediaper are removed and then cut into four equal length distributionzones. Each zone is then weighed to determine the weight of liquidcontained in each zone.

The liquid distribution results for representative fluted absorbentcomposite of the invention approaches ideality. The results indicatethat while the representative commercial storage cores accumulate liquidnear the site of insult, liquid is efficiently and effectivelydistributed throughout the fluted absorbent storage core.

While the preferred embodiment of the invention has been illustrated anddescribed, it will be appreciated that various changes can be madetherein without departing from the spirit and scope of the invention.

1. An absorbent composite comprising a fibrous matrix and superabsorbentmaterial, wherein the superabsorbent material is distributed directly inthe fibrous matrix in two or more bands, wherein each band is continuousalong the composite's length, wherein the regions between the bandscomprise fibrous liquid distribution zones, and wherein the fibrousmatrix comprises crosslinked cellulosic fibers.
 2. The composite ofclaim 1 wherein the distribution zones are substantially free ofsuperabsorbent material.
 3. The composite of claim 1 wherein the bandsare substantially parallel.
 4. The composite of claim 1 wherein thebands further comprise fibrous material.
 5. The composite of claim 4wherein the fibrous material comprises fibers selected from the groupconsisting of resilient fibers, matrix fibers, and mixtures thereof. 6.The composite of claim 1 wherein the fibrous matrix comprises fibersselected from the group consisting of resilient fibers, matrix fibers,and mixtures thereof.
 7. The composite of claim 6 wherein the resilientfibers are selected from the group consisting of chemically stiffenedfibers, anfractuous fibers, chemithermomechanical pulp fibers,prehydrolyzed kraft pulp fibers, synthetic fibers, and mixtures thereof.8. The composite of claim 7 wherein the chemically stiffened fiberscomprise crosslinked cellulosic fibers.
 9. The composite of claim 8wherein the crosslinked cellulosic fibers are crosslinked with acrosslinking agent selected from the group consisting of urea-based andpolycarboxylic acid crosslinking agents.
 10. The composite of claim 7wherein the synthetic fibers are selected from the group consisting ofpolyolefin, polyester, polyamide, and thermobondable bicomponent fibers.11. The composite of claim 10 wherein the polyester fibers arepolyethylene terephthalate fibers.
 12. The composite of claim 6 whereinthe matrix fibers comprise cellulosic fibers.
 13. The composite of claim12 wherein the cellulosic fibers comprise fibers selected from the groupconsisting of wood pulp fibers, cotton linters, cotton fibers, hempfibers, and mixtures thereof.
 14. The composite of claim 6 wherein theresilient fibers are present in the composite in an amount from about 10to about 60 percent by weight of the total composite.
 15. The compositeof claim 6 wherein the matrix fibers are present in the composite in anamount from about 10 to about 50 percent by weight of the totalcomposite.
 16. The composite of claim 1 wherein the superabsorbentmaterial is selected from the group consisting of superabsorbentparticles and superabsorbent fibers.
 17. The composite of claim 1wherein the superabsorbent material is present in an amount from about0.1 to about 80 percent by weight of the total composite.
 18. Thecomposite of claim 1 wherein the superabsorbent material is present inabout 40 percent by weight of the total composite.
 19. The composite ofclaim 1 wherein the superabsorbent material absorbs from about 5 toabout 100 times its weight in 0.9 percent saline solution.
 20. Thecomposite of claim 1 further comprising a wet strength agent.
 21. Thecomposite of claim 20 wherein the wet strength agent is a resin selectedfrom the group consisting of polyamide-epichlorohydrin andpolyacrylamide resins.
 22. The composite of claim 20 wherein the wetstrength agent is present in the composite in an amount from about 0.01to about 2 percent by weight of the total composite.
 23. The compositeof claim 20 wherein the wet strength agent is present in the compositein about 0.25 percent by weight of the total composite.
 24. Thecomposite of claim 1 having a basis weight of from about 50 to about1000 g/m².
 25. The composite of claim 1 having a density of from about0.02 to about 0.7 g/cm³.
 26. The composite of claim 1 wherein thefibrous matrix comprises crosslinked cellulosic fibers present in about45 percent by weight based on the total weight of the composite.
 27. Thecomposite of claim 1 wherein the fibrous matrix comprises wood pulpfibers present in about 15 percent by weight based on the total weightof the composite.
 28. The composite of claim 1 wherein the fibrousmatrix further comprises superabsorbent material.
 29. A wetlaidabsorbent composite comprising a fibrous matrix and superabsorbentmaterial, wherein the superabsorbent material is distributed directly inthe fibrous matrix in two or more bands, wherein each band is continuousalong the composite's length, wherein the regions between the bandscomprise fibrous liquid distribution zones, and wherein the fibrousmatrix comprises crosslinked cellulosic fibers.
 30. An absorbentcomposite, comprising a fibrous matrix and superabsorbent material,wherein the superabsorbent material is distributed directly in thefibrous matrix in two or more bands, wherein each band is continuousalong the composite's length, wherein the bands swell and form a flutedstructure upon contact with liquid, wherein the regions between thebands comprise fibrous liquid distribution zones, and wherein thefibrous matrix comprises crosslinked cellulosic fibers.
 31. Thecomposite of claim 30 wherein the composite has a width and a length andwherein the bands and liquid distribution zones alternate across thecomposite's width and extend along the composite's length.